Washing electrolytic capacitor sections



July 7, 1959 E. F. FREKKO WASHING ELECTROLYTIC CAPACIT OR SECTIONS Original Filed July 17. 1952 [ggienz Patented July 7, 1959 G ELECTROLYTIC CAPACITOR SECTIONS Eugene-Frekko, Westfild, 'NJ., assignor to Cornell- :Dubilier Electric Corporation, South Plainfield, -N.J., a corporation of 'Delaware Original application-July 17, 1952, Serial No. 299,348, now Patent No. 2,767,110, dated'Octo'ber 16, 1956. Divided and 'tliis application Dec'ember'27, 1955, Serial N0. 555,647

:1 claim. or. 134-144 Patent No. 2,767,110, dated Oct. 16, 1956.

Ask generally-known, an electrolytic capacitor consists of a film formed metallic ano'de and a metallic cathode separated from 'each other by an absorbent separator suchas paper or cloth, and wherein such absor-bent separator isimpregnated with a-film forming electrolyte.

Thefilm forming metallic anode is, because of practical and economical considerations, usuall-y'composed of aluminum, and 'similarly the -meta'llic cathode is also "composed-of aluminum for, in addition to theeconomic -considerations,the electrodes of'an electrolytic capacitor should be ofsubstantiallythe :sarne metal to prevent unwanted galvanic-action.

When aluminum electrodes are used in electrolytic capacitors, it .isessential in the production of high quality capacitors to'minimize the quantities of undesirable deleteriousimpurities. The,particular impurities which are most del-eteriousto the production of highquality electrolytic capacitors employing aluminum electrodes are those -materials which form anions by disassociation or by the-action of an electric current and are those of the chemical class consisting of chlorides, sulfides and sulfates.

.Inapresentday production of high quality electrolytic capacitors, extreme care is exercised in maintaining great cleanlinessof'the constituent elements of the capacitors, and .it is common in the production of such capacitors to wash .and purify the surfaces of'the electrodes andto select only. highpuritymaterialsand chemical ingredients. -lt is also necessary to eliminate contamination 'of the respective parts which .may resultfrom handling these parts in the actualassembly-ofthe capacitor. Such contamination is eliminated to aconsiderable degree by providing rubber-gloves for the operators engaged in the assembly ofuthe capacitors.

In the present practicemost-of the separator material consists of absorbent paper similar to blottingpaper, and

. in its manufacture only .paperapulp which meets rigid chemical analysis for freedom from impurities is used. :However, inthe manufacture of paper-.suitablefor electrolytic capacitor separators, -the felting process requires :the nse of large quantities of water. Thense of such large quantities of water precludes the employment of chemically pure-water such asdistilled or deionized water, and ingeneral the water supply for-the manufacture of paper is obtained from streams which are subject to variable-contamination during the several seasons of the -year. Thus,-some lots of absorbentseparator paper may be relatively free of deleterious impurities and other lots of! paper may be substantially unuseable for high quality electrolytic capacitors because of large quantities (Kimpurities. The paper separatormaterialmay be tested for impurity content at -the outer end ofeach roll, but such tests are not practical on inner-parts or throughout the entire length'of a roll of the "paper separator material during the winding of the-capacitor sections. However, it is possible thatsomewhere along-theroll 'of such material certain spots may have been-contaminated due to certain uncontrollable factors in the manufacture of the paper, such for-example as the water. Therefore, it is possible that'in spite of-the most vigorous inspection, a capacitor section roll is produced with'certain portions in it which have an impuritycontent higher than would be permissible for operation of such unit overthe long operating life required of such capacitors and at the higher temperatures required'during such life.

Since it was relatively-impracticahto test the paper rolls prior to their assembly into capacitor sections, some cleaning process was needed-forsubstantially removing impurities-after the electrolytic capacitor hadbeen completed except for the-impregnation with the electrolyte.

Therefore, it is an object of the present invention to substantially eliminate deleterious contamination incurred during the assembly or-manufacture of electrolytic capacitors, and to minimize-or'substantially eliminate impurities contained in oronthe-sur'faces oftlre various elements of electrolytic capacitors. I

Another'object of the invention-is-to minimize or substantially eliminatedeleterious ir'npuritiesfrom the separator material and'tomake; possible the use of separator material containing-a relatively high-degree of impurities or in which. the control bf the impurity content-was not completely reliable.

These and other objects of the invention will be appreciated from the following deseription.

The invention essentially' consistsof passing a cleaning agent through a wonnd capacitor section; prior to its impregnation with an electrolyte, whereby a washing and cleaning process is carried out, the-cleaning agent being subsequently removed from the capacitor section by means creatingtapressure differential between the :two ends of the capacitor section and by evaporation. Various means maybe msed-for accornplishing the cleaning operations, and several-cleaning agentsare' suitable.

For a more'completedescription of -the invention, reference is made to the drawings of oneform'of apparatus, wherein:

Fig. lisa side view partlyin-sectionof a centrifuge apparatus embodying the invention;

Fig. 2 is a cross-sectional,,.plan v-iew'oftheapparatus taken along thelinel-Q in Fig. r1;

.Fig. 3is an isomeric view of a removable basket elementin which t the capacitor sections-are held'during the centrifuge operation; and r Fig. 4 is an enlargedpend view ofa wound capacitor section prior to its-impregnation electrolyte.

The apparatusshowninFigs. l3, which is one'embodiment for carrying out theinvention, includes a supporting base l0, afixedohamberd1which is liquid tight and has aremovable cover 12. flhe-covertishinged at-13 andis provided with-a closuredevice 15. Adrain 16 is provided in thelowenpart of-thechamber 11. A perforated pipespray -17 is -slidably'rnounted in housing '19 in the centerof the cover 12 .andextends down through the cover into the chamber when .thecover is in closed position, as shown-in Fig. 1. Ihe slidable mounting for the pipe :17 permits it to .be -drawn upward, firom' the position shown in Fig. 1, so that when the cover is being opened and closed -ther'lower end of the pipedoes not strike theperforatedchamberlfi. 'The pipe17' is coupled to a flexible hose 18 on the outside of the cover 12.

A motor 20 is mounted'belowt-the chamber 11 and has a shaft 21 extending upwardly through the bottom of the chamber 11. The Shaft 21 is that with a turntable 22 at its upper end.

A perforated chamber 23 is fixed on the turntable 22 for rotation with said turntable and shaft when rotation is imparted to those members by the motor 20. The bottom and-the sides of the chamber 23 are formed with a plurality of perforations 25 through which liquid may pass. The upper end of the perforated chamber 23 is provided with a hood member 26 which extends inwardly from the peripheral walls of the chamber 23 and defines a relatively large, central opening.

Removable perforated baskets 27 are adapted to receive a plurality of wound capacitors 28 to be cleaned. The baskets are formed with perforated walls having perforations 30 through which liquid may pass. One side 31 of each of the baskets may beopen (Fig. 3), through which the capacitors may be received and removed. The removable baskets 27 are adapted to be positioned in the perforated chamber 23 "around the inner wall thereof with the wound capacitors disposed with their axes substantially radial to the axis of the perforated chamber 23 and with respect to the pipe spray 17. The arrangement of the baskets 27 is illustrated in Fig. 2. Spacer members 32 are provided between the baskets to maintain them in relatively fixed position during the rotation of the chamber 23. 1

Suitable means may also be provided for removably fixing the baskets in the arrangement shown in Fig. 2 to prevent their shifting around during the acceleration or deceleration of the centrifuge.

A suitable control apparatus may be provided for the -motor 20, at the side of the centrifuge apparatus, such as the control box 33 and control handle 35.

In order to clean the wound capacitors 28, they are placed in tiers in the baskets 27 in the manner shown in Fig. 3, and the baskets are thereafter placed in the perforated chamber 23, in the arrangement shown in Fig. 2, with the open sides 31 of the baskets facing the spray pipe 17. Handles 36 may be provided on the baskets 27 to facilitate the positioning and removal of the baskets in the perforated chamber. When the baskets 27 are in position and suitably. spaced around the inner wall of the chamber 23, in the manner shown, the cover 12 is closed to the position shown in Fig. l, and the locking device 15 engages latch 14 provided on the upper side of the chamber 11. The pipe spray 17 is slid downward to the position shown in-Fig. 1. Thereafter the motor 20 is started in order to rotate the perforated chamber 23. A cleaning agent is fed through the flexible hose 18 and is sprayed into the chamber 23 through the openings 37 disposed along the length and around the circumference of the pipe spray member 17. The sprayed cleaning agent impinges against the inner ends 38 of the wound capacitor sections 28 and is drawn through the longitudinal interstices 40 (see Fig. 4) of the wound capacitor sections 28 by centrifugal force. The cleaning agent passes axially through each of the capacitor sections and is thrown off at the outer ends 41 of said sections, thereafter passing through the perforations 30 in the outer walls 42 of the baskets and the perforations 25 in the chamber 23. The differential centrifugal pressure provides a means for forcing the cleaning agent through the wound capacitor sections, so that unwanted impurities on the surfaces of the electrodes and contained in the absorbent separators may be dissolved and carried off with the cleaning agent. As the cleaning agent is thrown outwardly through the perforations 25, they impinge upon the inner wall of the chamber 11 and collect in the bottom of the chamber and are drained off through the drain 16 which is connected by suitable means such as pipes 43 to a reservoir which is not shown.

It will be appreciated that the cleaning agent can be repurified or regenerated by distillation or other means, and may be reused for subsequent cleaning operations.

As an example of this means of forcing the cleaning '4 agent through a. wound capacitor section, it has been found that an mfd. 350 V. DC. electrolytic capacitor section having a size of approximately 1" diameter and a length of approximately 3%" may be suitably cleaned by arranging the section with its axis substantially radial in a centrifuge, applying a cleaning agent at a ratio of about 500 cubic centimeters over a period of approximately five minutes in a centrifuge chamber having an approximate size of 24" in diameter and a speed of approximately 1200 revolutions per minute. Such a size centrifugal chamber and speed will produce a differential pressure from the inner end, i.e. 38, to the outer end, i.e. 41, of approximately fifty pounds per square inch.

A suitable cleaning agent for this purpose can be any agent which has a dissolving action on the unwanted impurities. For example, it has been found that distilled water or chemically pure polyhydric alcohol, such as glycerine or ethylene glycol are satisfactory. However, the present preferred practice is to use an alcohol having relatively low evaporating temperature such as isopropyl alcohol.

After the cleaning agent has been-forced through the capacitor section for a suitable period of time, no further cleaning agent is sprayedthrough the pipe 17 However, the rotation of the centrifuge is continued for the purpose of expelling as much ofthe cleaning agent as possible from the interstices of the capacitor sections by the continued differential centrifugal pressure. Thereafter, the capacitor sections are removed from the centrifuge and any residual cleaning agent is allowed to evaporate. It will be appreciated that the evaporation can be accelerated by the use of heat or heat supplemented by an evacuating means.

Thereafter the dried capacitor sections may be impregnated with a film forming electrolyte of any suitable, well known composition, such as a mixture of ammonium borate and ethylene glycol. The process of impregnation can be accomplished in any well known manner, such as vacuum impregnation or centrifugal impregnation, or by soaking in the electrolyte. The electrolyte can be easily checked in large batches before impregnating the capacitor sections so that there is no problem in maintaining adequate purity at this phase in the manufacture of capacitors.

It will be appreciated that although the method and apparatus for forcing the cleaning agent through the Wound capacitor secti ns has been illustrated by a centrifuge, the cleaning action can also be performed by inserting a capacitor section in one end of a tube and forcing the cleaning agent through the tube and through the section or by any other suitable means in which a cleaning agent may be forced through a wound capacitor section, so that it can dissolve impurities on the surface of the electrodes and also dissolve impurities which may be in the absorbent separators and carry off such impurities.

In the operation of electrolytic capacitors, it is desirable to have as small an electrical leakage current as possible passing through the electrolyte, and unless the electrical leakage current remains below a certain maximum value, the capacitor will become heated during operation because of electrical resistance to the current flowing through the electrolyte. The heating of an electrolytic capacitor, because of these electrical losses, is cumulative, and the more elevated the temperature of the electrolyte becomes the less its specific resistance becomes, and the greater becomes the leakage current. Consequently, above a certain maximum leakage for a given size, the electrolytic capacitor may be subjected to a destructive cycle for the leakage will heat the section which will in turn increase the electrical leakage, thereby producing additional heat. This cycle continues until the capacitor is destroyed.

In an electrolytic capacitor section of the size specified above, the maximum leakage current which can be tolerted when the capacitor is operating at C. is about 5 milliamperes at: 350 v. Set forth below are test data indiproduced which are capable of operation at'elevated ambient temperatures such as-are required bymm m tion of electronic equipment.

Chart 1.- Te st data for ethylene-glycol asacleaning agent Uneleaned Cleaned Time 1 .2 .2 .2 .2 .2 .2 .3 .2 .2 .2 .2 .2 .2 .2 .2 .2 1.0 .5 .5 .3 .5 .3 .5 .2 .4 .2 .2 .2 .4 .2 .2 .5 1.8 1.2 .9 .5 1.0 .4 1.0 .4 .7 .3 .2 .3 .8 .4 .4 .8 10 4 3.3 1.5 3.8 1.6 4.5 1.4 1.3 .8 .2 .8 1.8 1.1 1.1 2.2 }All leakages over 20 me. Test discontinued 3:? i2 3:8 :3 2:8 g3 2:3

Chart 2.-Distilled water as a cleaning agent Uneleaned Cleaned .3 .2 .3 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 1.7 .8 2.0 1.0 .8 1.0 .4 .7 .7 .8 .6 1.0 .8 .8 1.7 1.5 2.8 1.2 3.0 1.6 1.0 1.0 .4 .3 .8 .8 .3 1.0 1.2 1.0 2.7 2.2 4.0 1.5 4.5 2.2 1.3 1.5 .5 .8 1.0 1.2 1.2 1.3 1.3 1.3 3.5 3.0 Leakage above 10 me. .5 .8 .2 .3 .3 .5 .4 .8 1.0 .8 2.3 1.8 discontinued. .5 .5 .2 .3 .4 .5 .3 .5 .5 .5 1.0 1.0

Chart 3.-Is0pr0pyl alcohol as a cleaning agent Uncleaned Cleaned .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .4 .3 .4 .5 .5 .3 .4 .4 .4 .4 .4 .4 .4 .4 .4 .4 1.4 1.2 1.3 1.2 1.7 1.0 1.5 1.3 1.0 .8 .8 1.2 .3 .8 .8 .8 3.4 2.3 2.7 3.5 7.0 6.5 4.0 2.5 1.2 1g 15 I7 15 19 I5 111 I6 110 Leakage above 10 m.e. Discontinu .2 .3 .2 .5 .2 .5 .3 .6 .2 .3 .2 .3 .15 .3 .15 .25

Referring to the above charts it will be noted that in In accordance with the provisions of the patent statutes, all cases the uncleaned comparative sections approached have herein described the principle of operation of the the destructive temperature and leakage cycle (Le. somelnvention, together with the elements 'WhlCh I now conthing above 5.0 milliamperes) at between 1% and 2 sider the best embodiments thereof, but I desire to have hours and the cleaned capacitor sections had not it understood that the structure disclosed is only illusapproached the destructive lialclage tempelrature dcyl lclg trative an :1 the ilniviention cgnbe garried out1 by other after four hours in the case 0 c arts an an a means. 80, w e it 1s esrgne to use t e various not approached the destructive leakage temperature cycle features and elements in the combinations and relations after 480 hours in the case of chart 3. described, some of these may be altered and modified A further method at clealing the catpaci ct gl l l1"wliltlilout interfering with the more general results outwhich has been foun sans actory 1s 0 immerse e e wound sections in a cleaning agent and thereafter draw Having thus described my invention, I claim: the cleaning agent from interstices of wollnd Apparatus for removing impurities from convolutely Sections y means of a centrifuge Suitable eYacuatmg Wound electrolytic capacitors prior to their impregnation pp In the use of this methods however, It l/ with electrolyte comprising a liquid impervious stationary found necessary to immerse the sectlons 1n the cleamng cylindrically shaped basket member having an upwardly agent more than one tlme. directed open end, a manually displaceable cover mem- Dllriflg tests With regard the effectlvqness of the use ber pivotally mounted on said stationary basket mem- Of a Cleaning ?ge11t, the cleaning agent which was thrown ber for selectively closing the open end thereof, a liquid from the sections was collected and tested to determlne permeable cylindrically shaped basket member disposed the qegree i cleanmg whlql a z f concentrically within said stationary basket member and first mlmerslon of i q m g i p rotatable about its longitudinal axis, a non-rotatable the wlthdrawal of t e c ealimg .agen mm 6 sec 0 cleaning agent spray pipe mounted on said cover member test showed that the chlorlde 1011 content in a 10 cubic centimeter sample of the d eam-ng agent was 3 p P In so as to be hneally displaceable relative thereto and selec- (parts per million). The second wash showed a .5 p.p.m. 'flvely f F 9 of f rotatable Pasket chloride, and the third wash gave no tests for chloride ber for dlrectmg hquld cleaning agent 'l'adlally mward at 31L the periphery of said rotatable basket member, spaced It will, therefore, be appreciated from an examination 8 y i means i p on the r p y of of the above charts and the tests related above that the i rotate has et mem er extendms mwardly contamination and impurities which are in large part toward the longitudinal axis thereof, each adjacent pair responsible for electrical losses in an electrolytic capaciof said spaced tnangularly shaped means providing two tor, and which may ultimately cause the failure of the opposed parallel walls defimng a capacitor holder receivcapacitor, may be eliminated. It has been found that mg space disposed therebetween, a hquid permeable by cleaning capacitor sections in accordance with this capacitor holder sized and shaped to be insertably mountinvention, high quality electrolytic capacitors can be ed in each of said capacitor holder receiving spaces, each 7 f of said eapacitor holders being shaped to support a plu- References Cited in the file of this patent :ratityjbgjwgind capacitor units remote from said spray ,o 1 N ED STATES PATENTS pi'pewi eair'es' thereof disposed substantially radially of the axis of rotation of said rotatable basket mernber, 'a g if" and means for eifecting high speed rotation of said rotat- 5 21240s2 c1 1938 able basket member relative to said spray pipe whereby, V v 7 t "'7 Z 1939 eleettttte eteet emitted thetety tetettteee eeetttet the etet 212561663 Brewerjjjjjjjjjjjjjjsepta; 1941 of said capacitors and is longitudinally forced therethrough by the forces generated by the rotation of said t m FOREIGN PATENTS rotatable basket member. 7 357,919 Great Britain Oct. 1, 1931 

